Method of acidulating phosphate rocks and reaction-promoting agents therefor



United States Patent" METHOD OF ACIDULATING PHOSPHATE ROCKS ANDREACTION-PROMOTING AGENTS THERE- FOR Abraham Goldhaar, Los Angeles,Calif., assignor to Universal Detergents, Inc., Fort Worth, Tex., acorporation of Delaware No Drawing. Application October 9, 1953, SerialNo. 385,277

3 Claims. (Cl. 71-40) This invention is directed to improvements inmethods of acidulating phosphate rock whereby by formation of readilysoluble and available phosphoric acid compounds is expedited andincreased and many operating, economic and physical benefits attained.

that present methods are time-consuming and burdensome in that theacid-treated phosphate rock tends to stick to led by the total P205content reported.

Incompletely reacted phosphate rock often indicates that themanufacturer is losing money; fluorides are lucrative by-product andincomplete reaction results in incomplete recovery of fluorides as wellas incomplete conversion of phosphates to soluble form.

the curing piles and has to be hterally blasted to permit its removalfrom the curing piles. v

This invention is based upon the discovery that certain phate rock,greatly increase the rate of reaction, permit the formation of solublephosphates to; reach higher levels within a shorter period of time,increase the recovery of 2,786,746 Patented Mar. 26, 2 4 a fluorine andits compounds and acids and produce a better grade of superphosphatewith concomitant advantages 284,041, filed April 24, 1952, by James w.Putt and en-: titled Manufacture of Synthetic Detergents.

phate by acidulation of phosphate rock. 7 It is an object of thisinvention to disclose and providea In continuous methods, the rock andacid are fed continuously into a paddle-type mixer, discharged therefrominto a den and continuously cut out of the den. The reactions may beindicated as:

CaF2+H2SO4 CaSO4+2HF 4HF+SiO2 SiF4+2H2O The silicon tetrafluoridegenerally escapes before hydrofiuosilic acid is formed. The generalsolubilizing reaction may be indicated ast but this ideal condition isnot attained and monocalciurn; phosphate and dicalcium phosphate,

cium metaphosphate, both of'which are sparingly soluble and not wellregarded. I 1 The reaction-promoting agent for use in this process inaccordance with this invention is'an essentially non-hygro" 'orouseonditio is, the remaining '92%-88% ma gent bath of the sulfuric acid-In addi i n scopic, water-soluble, alkali metal salt of a sulfonatedmixture of alkylated derivatives of naphthalene containing methyl groupsand/or alkyl groups with 8 to 12 carbon atoms. Such mixture may alsocontain relatively small quantities of alkali metal salt of naphthalenesulfonate. Desirable alkyl groups areintrodueed 'by reacting thesuitable aromatic hydrocarbons with olefins such as nonylene,diisobutylene and tri-isobutylene. Suitable catalysts, as for example,sulfuric acid, may be used for this purpose. The preferredreaction-promoting agent is readily soluble .in water, producingfree-flowing, substantially transparent solutions even at -55%-60%concentras tion. Properties of such solutions (which may be termedcolloidalj are unaiiected b filtration. The solution are ot d s r ye rchan d y di ut f i n c.- phospho c d an ble, hom n o s colloidal us-Pens ons r reaction-promoting agent are added to sulfuric acid, when 80%H259 is present in the final aqueous suspension. Moreover, it does notprecipitate to any material extentin the'presence of calcium ions;.tests performed by the addition of calcium chloride to aqueoussolutions of the agent show that only between 8% to 12% of thereaction-promoting agent is preeipitated under the most rigmaintainingits activity and effectiveness. The process by which the treating agentis produced is described in the copending application referred tohereinabove.

'In carrying out the process of this invention, the reaction-prornotingagent may be added to the sulfuric acid, but preferably an aqueoussolution of the reaction-prois f rst formed and such dilution watersolution is then added to the acid resulting in a mixture suitable foracidulating the phosphate rock. Ordinarily from 1600 to 2000 lbs. of 52B. acid are used per ton of A reagent of this invention is added at therate of 0.25 to 1.0 lb. per ton ofrock. Mixing of the acid with thephosphate rock may be carried out in the available equipment and in theusual manner, but it will be found that reaction is much more rapid andcomplete. The evolution of silicon tetrafluoride and hydrogen fluorideis accelerated and recovery thereof is materially increased; mixing panscan be dumped within a shorter period of time and with greater ease; thereacted mixture is homogeneous and dryer than usual in the den; it doesnot set up into hard unmanageable masses in the den, does not appear tostick to walls or equipment and can be removed with greater facility.The curing time is reduced very appreciably and conversion to solubleforms is much higher. The resulting superphos phate does not cake orsolidify and is easily handled from curing pile to bagging for shipment.

Commercial runs, made without an agent, with the reaction-promotingagent specifically mentioned herein and with a commercial surface-activeagent salt of sulfonated alkl benzene, the alkyl group being largelydodecyl), have convincingly shown the beneficial results which fiow fromthe process of this invention. Averages of many commercial runs, allother factors being the same as far as possible under plant conditions,showed that normal operations, without a reaction-promoting agent,produced a conversion of 88.9% in the material discharged from the denwhereas the conversion with the reaction-promoting agent averaged 92.1%.The material from the den was dryer; average without agent 10.47% 1 120,whereas the average with the agent was 9.10% H2O. The commercialsurface-active agent referred to herein was tried and was foundincapable of producing thesarne results; the average moisture con-tent,ex den, was 10.79% and the average conversion 90.5%. The improvedresults with the reaction-promotin agent may be due in part at least tothe fact that it is highly hydrophilic and that its sulfonic acid iseasily suspended n the. te m. of myriads of fine particl s throug out tA it maybe noted (alkali metal that the commercial surface-active agent,because of its practically incomplete solubility in acid and inabilityto form homogeneous suspension therein or for other reasons, producedtarry, dark blotches in the den material.

The specific group of reaction-promoting agents defined for use in thisinvention, exhibit surface active characteristics, which are effectivelyretained in the presence f ulfuri ni ri nd phosphoric acids or in h p nof free calcium ions. They quickly dissolve or disperse in the statedacids and are therefore of value in the production of uitrated phosphaterocks as well as normal superphosphate (produced with sulfuric acid) andthe socalled triple phosphate.

All changes, modifications, adaptations and advantages coming within thescope of the appended claims are embraced thereby.

! claim:

1. A method of expediting and increasing the rate of formation ofsoluble phosphates during the manufacture of superphosphate. by the acidtreatment of phosphate rock, which comprises: forming an aqueoussolution of a reaction-promoting agent comprising an alkali metal salt.of a sulfonated mixture of naphthalene and alkylated derivatives ofnaphthalene, containing methyl groups and alkyl groups with 8 to 12carbon atoms; adding said aqueous solution to sulfuric acid to produce amixture containing between about 65% and acid in which thereaction-promoting agent is adapted to form a homogeneous and finedispersion without separation; and bringing the dispersion of sulfuricacid and reactionpromoting agent into contact with phosphate rock inquantity sufficient to i troduce from about 0.25 to 1.0 lb. of agent perton of such rock, whereby the superphosphate so obtained does not set toa hard mass during curing.

2. A method ofexpediting the formation of superphosphate in a soft,readily workable condition by the acid treatment and curing of phosphaterock, which comprises: forming an aqueous solution of areactionprornoting agent composed of water-soluble, alkali metal saltsof a sulfonated mi ture of naphthalenes and their alkylated derivativescontaining alkyl groups with 8 to 12 carbon atoms, more than of saidagent remaining active and in solution in the presence of calcium ions;adding said aqueous solution to sulfuric. acid to produce a solutioncontaining between about 65% and 80% acid in whichrthereaction-promoting agent is adapted to form a homogeneous and finedispersion without separation; and bringing the dispersion of sulfuricacid and reactionpromoting agent into contact with phosphate rock,whereby the superphosphate so obtained does not set to a hard m ssduring curing- 3. A method of expediting the formation of superphosphatein a soft and workable condition by the acid treatment of phosphate rockwhich comprises: forming an aqueous solution of a reaction-promotingagent com- PQSfid'Q Water-soluble alkali metal salts of a sulfonatedmixture of naphthalenes and their alkylated derivatives containing alkylgroups with 8 to 12 carbon atoms, more than. 8.5% of Said agentremaining active and in solution in the presence of calcium ions; addingsaid aqueous solution to acid to he used in the acid treatment ofphosphate rock to form .a homogeneous and fine dispersion of thereaction-promoting agent in such acid; and bringns e di persion. i o conact with pho pha r ck, wh reby the ,superphosphate so obtained does notset to a ar ma s during cur ng- References Cited in the file of thispatent UNITED STATES PATENTS 1,901,506 fiunther' nfla Mar. 14, 19332,213,620 Bancroft .et a1. Sept. 3, 1940 2,218,695 Leathcnnan Oct. 221940 2,418,203 Apr- 1, 9 2,557,730 r V, V June 19, 1.951 2, 55,530Nevisou T----.-- O 1 9

1. A METHOD OF EXPEDITING AND INCREASING THE RATE OF FORMATION OFSOLUBLE PHSOPHATES DURING THE MANUFACTURE OF SUPERPHOSPHATE BY THE ACIDTREATMENT OF PHOSPHATE ROCK, WHICH COMPRISES: FORMING AN AQUEOUSSOLUTION OF A REACTION-PROMOTING AGENT COMPRISING AN ALKALI METAL SALTOF A SULFONATED MIXTURE OF NAPHTHALENE AND ALKYLATED DERIVATIVES OFNAPHTHALENE, CONTAINING METHYL GROUPS AND ALKYL GROUPS WITH 8 TO 12CARBON ATOMS; ADDING SAID AQUEOUS SOLUTION TO SULFURIC ACID TO PRODUCE AMIXTURE CONTAINING BETWEEN ABOUT 65% AND 80% ACID IN WHICH THEREACTION-PROMOTING AGENT IS ADAPTED TO FORM A HOMOGENEOUS AND FINEDISPERSION WITHOUT SEPARATION; AND BRINGING THE DISPERSION OF SULFURICACID AND REACTIONPROMOTING AGENT INTO CONTACT WITH PHOSPHATE ROCK INQUANTITY SUFFICIENT TO INTRODUCE FROM ABOUT 0.25 TO 1.0 LB. OF AGENT PERTON OF SUCH ROCK, WHEREBY THE SUPERPHOSPHATE SO OBTAINED DOES NOT SET TOA HARD MASS DURING CURING.